(a) Field of the Invention
The present invention relates to a robot and, more particularly, to a telescopic system for a robot that can obtain a predetermined stroke by providing a plurality of modules that are disposed to be movable with respect to one another.
(b) Description of the Related Art
U.S. Pat. No. 4,682,930 discloses a conventional telescopic system for a robot movable up and down. This will be described with reference to FIG. 1.
As shown in that drawing, a motor 6 is fixed in a stationary frame 1. A driving pulley 36 is fixed on a driving shaft of the motor 6. The driving pulley 36 is connected to a driven pulley 31 via a timing belt 32 so that the driven pulley 31 is rotatable relative to the stationary frame 1.
In addition, a spline shaft 33 is inserted into the driven pulley 31 such that it is movable in an axial direction but is not rotatable relative to the driven pulley 31. The spline shaft 33 is rotatably supported on an intermediate frame 7 through bearings.
Fixed on the stationary frame 7 is a first nut 4 to which a first screw 5 is coupled, the first screw 5 being designed to linearly move while rotating.
Coupled to the intermediate frame 7 through bearings is a second nut 8 which is rotatable but not movable linearly. Coupled to the second nut 8 is a second screw 9 which is linearly movable while rotating. The second screw 9 is rotatably supported on a movable frame 10.
In addition, pulleys 34, 11 and 12 are coupled to the spline shaft 33, the first screw 5, and the second screw 9, respectively. The pulleys 34, 11 and 12 are interconnected by a timing belt 35.
In the above described conventional telescopic system for a robot, the driving force of the motor 6 rotates the spline shaft 33 through the driving pulley 36, the timing belt 32 and the driven pulley 31. Rotational force of the spline shaft 33 rotates simultaneously both the first and second screws 5 and 9 through the pulleys 11 and 12 interconnected by the pulley 34 and the timing belt 35. Accordingly, the first and second screws 5 and 9 linearly move while undergoing rotation by the first and second nuts 4 and 8, thereby conveying a chuck 3 fixed on the movable frame 10 to a predetermined location.
A serious drawback of the above described conventional telescopic system is the complexity of the structure thereof That is, to move the intermediate frame 7 and the movable frame 10 up and down, the spline shaft 33 for transmitting the driving force of the motor 6 to the screws 5 and 9 and the pulleys 31 and 34 coupled to the spline shaft 33 must be specially provided, as do the nuts 4 and 8 and the screws 5 and 9. Therefore, when more than two stages of frames are expandably provided, the structure becomes that much more complicated, and a size and weight are increased. Particularly, during the operation of the system, a high load is applied to the stationary frame 1, deteriorating the reliability of the system.
The present invention has been made in an effort to solve the above problems.
It is an objective of the present invention to provide a telescopic system for a robot that can obtain a predetermined stroke by providing a plurality of modules that are disposed to be movable with respect to one another, yet have a simple structure.
To achieve the above objective, the present invention provides a telescopic system for a robot comprising a stationary module having a motor connected thereto, a rotational shaft rotated by a motor, the rotational shaft being mounted in the stationary module, a movable plate located in the stationary module and operatively associated with the rotational shaft to ascend and descend according to a direction of rotational motion of the rotational shaft, and a movable module mounted on the movable plate to extend away from and retract into the stationary module as the movable plate ascends and descends.
Preferably, the rotational shaft is provided with a spiral groove, and the movable plate has a screw nut associated with the spiral groove of the rotational shaft to ascend and descend as the rotational shaft rotates. The screw nut is provided at an inner circumference with a spiral groove corresponding to the spiral groove of the rotational shaft, and a plurality of balls are disposed within a space defined by the spiral groove of the screw nut and the spiral groove of the movable plate.
Further preferably, the stationary module comprises upper and lower plates, and the rotational shaft comprises an upper end rotatably supported on the upper plate of the stationary module and a lower end rotatably supported in a supporting body mounted on the lower plate of the stationary module. A plurality of vertical blocks are disposed between the upper and lower plates to support the upper plate, each block is provided with a projected rail, and the movable plate of the stationary module is provided with a guide groove associated with the rail such that the movable plate is guided by the projected rail when ascending and descending.
The motor comprises a driving shaft on which a driving pulley is mounted, and the rotational shaft comprises a driven pulley, the driving pulley and the driven pulley being interconnected by a belt.
A rotational force transmitting pulley is mounted on the rotational shaft of the stationary module such that the rotational force transmitting pulley ascends and descends together with the movable plate and rotates together with the rotational shaft. The movable module comprises a rotational shaft on which is mounted a rotational force receiving pulley connected to the rotational force transmitting pulley by a belt, and a movable plate mounted on the rotational shaft to ascend and descend as the rotational shaft of the movable module rotates. Finally, a sub-movable module is mounted on the movable plate of the movable module to expand away from and retract into the movable module as the movable plate of the movable module ascends and descends. The rotational shaft of the stationary module is provided with a linear groove associated with a spline nut supported on the movable plate of the stationary module, and the rotational force transmitting pulley is fixedly coupled to the spline nut.
The spline nut is provided with a ball receiving groove corresponding to the linear groove, and a plurality of balls are received in a space defined by the ball receiving groove and the linear groove.
Preferably, the movable module comprises an upper plate on which the rotational shaft of the movable module is rotatably supported, a plurality of blocks are disposed between the movable plate of the stationary module and the upper plate of the movable plate to support the upper plate of the movable module, each of the block is provided with a projected rail, and the movable plate of the movable module is provided with a guide groove associated with the rail such that the movable plate is guided by the projected rail when ascending and descending.
According to another aspect of the present invention, a telescopic system for a robot comprises a first stationary module, a motor associated with the first stationary module, a first rotational shaft in the first stationary module, and a first coupling means for coupling the motor to the first rotational shaft to rotate the first rotational shaft in the first stationary module. The system also includes a second movable module telescopically received in the first stationary module, a second rotational shaft in the second movable module, and a second coupling means (a) for coupling the first rotational shaft to the second movable module such that the second movable module and the second coupling means ascend and descend together according to a rotational direction of the first rotational shaft and (b) for coupling the rotational movement of the first rotational shaft to the second rotational shaft. The system then further comprises a third movable module telescopically received in the second movable module, and a third coupling means (a) for coupling the second rotational shaft to the third movable module such that the third movable module and the third coupling means ascend and descend together according to a rotational direction of the second rotational shaft.
In this other aspect of the invention, the second coupling means includes a rotational force transmitting pulley mounted for rotation with the first rotational shaft and for axial movement along the first rotational shaft, a rotational force receiving pulley mounted for rotation with the second rotational shaft, a belt interconnecting the force transmitting and receiving pulleys, and a movable member mounted for non-rotation on the first rotational shaft and connected to the second movable module so as to ascend and descend as the first rotational shaft is rotated and hence to similarly move the second movable module connected thereto.